1. Field of the Invention
This invention generally relates to a high-frequency heating apparatus and, more particularly, to a high-frequency apparatus suitable for a cooking apparatus such as a microwave oven, an induction heating cooker, or their composite cooker.
2. Description of the Related Art
In general, as a cooker utilizing high-frequency heating, a microwave oven, an induction heating cooker, and a composite cooker having functions of these microwave oven and induction heating cooker are used. Such a high-frequency cooker includes an independent or common inverter circuit to supply a drive power to a heating operation section.
More specifically, by employing the inverter circuit in such a high-frequency heating (cooking) apparatus, a heating output can be continuously controlled, and a high-frequency power allows use of a light and small-sized high-voltage transformer in a heating operation section (in particular, in a microwave oven).
The high-frequency heating apparatus employing an inverter circuit has some problems to be solved.
One problem is that a main controller for controlling the entire apparatus and an inverter controller for controlling the inverter circuit in response to a command from the main controller are required. A switching timing detector for detecting an effective switching timing of switching elements in the inverter circuit is also required. In addition, an oscillation circuit for outputting a sawtooth signal, a pulse modulation circuit for modulating the pulse width of an output from the oscillation circuit in response to an output set signal, and the like are required when the inverter controller is of analog type, thus causing a complicated arrangement and high cost.
Another problem of this apparatus is that a countermeasure against a high-voltage fault from the inverter circuit must be taken to effectively protect the main and inverter controllers.
In a conventional high-frequency heating apparatus employing the inverter circuit, however, the above problems have not been effectively solved. For this reason, in a future high-frequency heating apparatus employing an inverter circuit, it is urgent that the above problems are effectively solved.